1. Field of the Invention
This invention relates to an ignition distributor for internal combustion engine, and more particularly to an ignition distributor for internal combustion engine with reduced generation of radio noise.
2. Description of the Prior Art
Generally, internal combustion engines having an electric ignition system generate radio noise in a wide frequency range, which disturb radio broadcasting service, television broadcasting service and other kinds of radio communication systems. Particularly, the radio noise from the internal combustion engines of vehicles gives a disturbance to electronic appliances now provided on the vehicles for versatile applications and gives an adverse effect on the vehicle running. One of the noise generation sources is an electric discharge at the ignition distributor for the internal combustion engine.
Attempts have been so far made to suppress the noise generation at the ignition distributor, one of which is to provide a resistor of a few K.OMEGA. at the intermediate part of a rotor electrode in the ignition distributor to suppress generation of radio noise with high frequency. However, a discharge voltage is high between the rotor electrode and the stationary electrode and an energy loss during the electric discharge is high in such an attempt, resulting in a less effect on suppression of radio noise generation.
Another attempt is to provide a resistor or a dielectric as projected at the tip end of the metallic rotor electrode, where a precursor electric discharge takes place between the resistor or the dielectric and the stationary electrode, and the main electric discharge then takes place therebetween. That is, the electric discharge energy can be reduced, but no effect on oscillation suppression of the main electric discharge current can be obtained, and a less effect on reduction in the radio noise generation can be attained.